1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to an integrated circuit having integrated inductors, and more particularly to an integrated circuit having integrated inductors that provide high inductance and a high quality factor by laying out the integrated inductors so as to intensify magnetic flux induced by electric currents flowing along the inductors according to applied differential signals.
2. Description of the Related Art
Primarily, an integrated inductor is a crucial passive component for an integrated circuit for the sake of impedance matching, and thus occupies the largest area over the integrated circuit. Since the impedance is a frequency function, the size of the inductors should increase in proportion to the decrease of the operating frequency in order to obtain the same impedance. Disadvantageously, the increasing size of the integrated circuit tends to raise the unit cost of the circuit manufacturing. In this respect, various attempts have been made to develop an integrated inductor small in size and with high inductance and a high quality factor.
FIG. 1 is a side sectional view of a related art integrated circuit having integrated inductors, which is disclosed in U.S. Pat. No. 6,593,201. Referring to FIG. 1, an insulative metal layer 10, which is supported by a substrate 100, receives first inductors 12 and second inductors 14 that are arranged vertically. Hence, not only the size of the integrated circuit can be reduced, but the inductance can be increased as much as the mutual inductance by the magnetic coupling. However, the characteristics of the inductors 14 disposed under the inductors 12 are subject to degradation due to characteristics of the complementary metal oxide semiconductor (CMOS) process, and the quality factor may deteriorate. Additionally, taking account of the configuration alone in which a single signal is applied, the circuit where differential signals are applied requires doubling the size of the inductors.
FIG. 2 is another circuit having integrated inductors, which is disclosed in U.S. Pat. No. 6,549,077. Referring to FIG. 2, a drain inductor 21 is coupled to a drain terminal of a transistor 20, a gate inductor 24 is coupled to a gate terminal of the transistor 20 to apply a RF input signal, and a source inductor 27 is coupled to a source terminal of the transistor 20. With the above configuration, the electric current flows in the same direction to obtain the magnetic coupling so that the direction of the magnetic flux of each inductor 21, 24, and 27 is identical to the current direction. As a result, the inductance can be increased and the size of the integrated circuit can be reduced.
However, disadvantageously, since the transistor 20 is disposed substantially outside the square loop formed by the inductors 21, 24, and 27, the lead line is lengthened and parasitic components may increase. Also, as illustrated in FIG. 1 in which only the configuration with the single signal applied is considered, the circuit with the differential signals applied requires the inductors to be double-sized.